Optical birefringence imaging of the phase transition of K[sub2]Mn[sub2](SO[sub4])[sub3].

The present paper reports on the observation of the optical birefringence as a function of temperature of the langbeinite-type crystal K[SUB2]Mn[SUB2](SO[SUB4])[SUB3] by using an imaging version of the so-called rotating-polarizer method. This method provides separates moving images of the orientation of the optical indicatrix and the magnitude of the optical anisotropy, showing the domain-wall behaviour during temperature changes. Somenew results o the domain behaviour of the phase transition of K[SUB2]Mn[SUB2](SO[SUB4])[SUB3] have been obtained. It is concluded that the sample single crystal consists of local regions, indicating the coexistence of two phases in this langbeinite-type crystal. [ABSTRACT FROM AUTHOR]